Volvo Repair: 97 960 p0172, intake manifold gasket, flame trap

Question
Hi Regis,
I've checked vacuum lines, replaced air filter, sp. plugs,flame trap and i've checked resistance on both o2 sensors which both of them are out of limits. Could they fail @ the same time? Also the car idle rough at park when its operating at normal temp. Could also be the intake manifold gasket? Thanks for your help.

Answer
this code is a generic code and not  a volvo one so I do not know what it means.there could be a leak at the intake  manifold gasket  they do go bad on this model.spray the intake especially near #1 cylinder with a carb. or throttle cleaner and listen for a change in the idle if it does it is leaking.